1. Field of the Invention
The present invention is generally directed to providing reliable cooling systems for computer systems or for any electronic system requiring cooling. More particularly, the present invention is directed to the cooling of an enhanced test head which contains a very dense electronic package designed for test equipment manufacturers to test both logic and memory packaged products.
2. Prior Art
The test head electronics are required to perform these tasks in the shortest possible time and therefore particularly high heat fluxes are generated in the electronic package. Innovative solutions are necessary to handle these high heat fluxes and still maintain the integrated circuits within temperature specifications.
A typical test head preferably occupies a 15".times.30".times.30" volume and generates approximately 8,000 watts of heat. This heat flux must be continually removed from this small volume to maintain integrated circuit temperatures at acceptable levels. To convey this heat from the test head an enhanced cold plate mated through conduction cooling to the electronic cards was developed.
A refrigeration system employing a single cold plate which preserves flow isolation between the fluids in the redundant systems. In another aspect of the present invention, there is provided a combination of air and redundant refrigeration cooling for an electronic device such as a mainframe or server processing unit disposed within a cabinet possibly along with other less thermally critical components. In yet another aspect of the present invention, there is provided additional cold plates, each with its own array of electronic circuit cards to be cooled. The entire assembly is mounted on an articulated arm for movement to and from multiple test sites. The enhanced test head is capable of operating continuously in a variety of ambient conditions and under a variety of thermal loads.
In recent years, the semiconductor industry has taken advantage of the fact that CMOS circuits dissipate less power than bipolar circuits. This has permitted more dense packaging and correspondingly faster CMOS circuits. However, almost no matter how fast one wishes to run a given electronic CMOS circuit chip, there is always the possibility of running it faster if the chip is cooled and thermal energy is removed from it during its operation. This is particularly true of computer processor circuit chips and even more particularly true of these chips when disposed within multi-chip modules which generate significant amounts of heat. Because there is a great demand to run these processor modules at higher speeds, the corresponding clock frequencies at which these devices must operate become higher. In this regard, it should be noted that it is known that power generation rises in proportion to the clock frequency. Accordingly, it is seen that the desire for faster computers generates not only demand for computer systems but also generates thermal demands in terms of energy which must be removed for faster, safer and more reliable circuit operation. In this regard, it is to be particularly noted that, in the long run, thermal energy is the single biggest impediment to semiconductor operation integrity.
In addition to the demand for higher and higher processor speeds, there is also a concomitant demand for reliable computer systems and electronics. This means that users are increasingly unwilling to accept down time as a fact of life. This is particularly true in the demanding high pressure environment of electronic test equipment. Reliability in air-cooled systems is relatively easily provided by employing multiple air-moving devices (fans, blowers, etc.). Other arrangements which incorporate a degree of redundancy employ multiple air-moving devices whose speeds can be ramped up in terms of their air delivery capacity if it is detected that there is a failure or need within the system to do so. However, desired chip-operating power levels are nonetheless now approaching the point where air cooling is not the ideal solution for all parts of the system in all circumstances. While it is possible to operate fans and blowers at higher speeds, this is not always desirable for acoustic reasons. Accordingly, the use of direct cooling through the utilization of a refrigerant and a refrigeration system becomes more desirable, especially if faster chip speeds are the goal.
While certain electronic components or modules produce relatively large amounts of thermal energy, it is often the case that these modules are employed in conjunction with other electronic circuit components which also require some degree of cooling but do not operate at temperatures so high as to require direct cooling via a cold plate and/or refrigerant system. If modules of varying thermal energy output are employed in the same system, it is therefore desirable that the cooling systems employed for the lower thermal output modules be cooled in a manner which is compatible with cooling systems employed for the higher temperature modules. To the extent that a degree of cooperation between these systems can be provided, the net result is a system which is even more reliable and dependable. Nonetheless, these dual cooling modalities may be accommodated within a single electronic card assembly.
There are yet other requirements that must be met when designing cooling units for computer systems, especially those which operate continuously and which may in fact be present in a variety of different thermal environments. Since computer systems run continuously, so must their cooling systems unlike a normal household or similar refrigerator which is operated under a so-called bang-bang control philosophy in which the unit is alternating either totally on or totally off. Furthermore, since large computer systems experience, over the course of time, say hours, variations in user load and demand, the amount of heat which must be removed also varies over time. Therefore, a cooling unit or cooling module for a computer system must be able not only to operate continuously but also be able to adjust its cooling capability in response to varying thermal loads.